Sestamibi parathyroid scan

A sestamibi parathyroid scan is a procedure in nuclear medicine which is performed to localize parathyroid adenoma, which causes Hyperparathyroidism. Adequate localization of parathyroid adenoma allows the surgeon to use a minimally invasive surgical approach. Tc99m-sestamibi is absorbed faster by a hyperfunctioning parathyroid gland than by a normal parathyroid gland. This is dependent on several histologic features within the abnormal parathyroid gland itself. Sestamibi imaging is correlated with the number and activity of the mitochondria within the parathyroid cells, such that oxyphil cell parathyroid adenomas have a very high avidity for sestamibi, while chief cell parathyroid adenomas have almost no imaging quality at all with sestamibi. Some researchers have also attempted to quantify or characterize the imaging capabilities of parathyroid glands by the MDR gene expression. Approximately 60 percent of parathyroid adenomas may be imaged by sestamibi scanning. The natural distribution of causation for primary hyperparathyroidism is roughly 85% solitary adenomas, 10-15% diffuse hyperplasia, and 1% cancer. Imaging is not as reliable in patients with multiglandular parathyroid disease. In addition, size limitation of the abnormal gland can limit the detection by radionuclide scanning. SPECT (three-dimensional) imaging, as an adjunct to planar methods, may increase sensitivity and accuracy, especially in cases of small parathymic adenomas. By using a gamma camera in nuclear medicine, the radiologist is able to determine if one of the four parathyroid glands is hyperfunctioning, if that is the cause of the hyperparathyroidism. Theoretically, the hyperfunctioning parathyroid gland will take up more of the Tc99m-sestamibi, and will show up 'brighter' than the other normal parathyroid glands on the gamma camera pictures, especially because of the internal biofeedback loop within the body with calcium inherently feeding back to calcium-receptors and inhibiting parathyroid hormone production within the normal parathyroid glands.